MicroRNAs (miRNAs) are a class of small highly conserved RNAs that provide widespread expressional control through the translational repression of mRNA. MiRNAs have fundamental roles in the regulation of intracellular processes, and their importance during malignant transformation and metastasis is becoming increasingly well recognized. An important event in the metastatic cascade is epithelial to mesenchymal transition (EMT), a reversible phenotypic switch over, which endows malignant epithelial cells with the capacity to break free from one another and invade the surrounding stroma. Our understanding of EMT has been significantly improved by the characterization of miRNAs that influence the signalling pathways and downstream events that define EMT on a molecular level. Here, we detail the role of miRNAs in EMT, and in doing so demonstrate their importance in the early stages of the metastatic cascade; we discuss a significant body of data that suggest new opportunities for drug development, and we highlight critical knowledge gaps that remain to be addressed. Small highly conserved non‐coding microRNAs (miRNAs) regulate the expression of a wide range of genes involved in tumourogenesis and metastasis. Epithelial to Mesenchymal Transition (EMT) and the reverse process Mesenchymal to Epithelial Transition (MET) are key events in the metastatic cascade suggesting that plasticity is a prerequisite for cancer cells capable of completing the metastatic journey. Here we demonstrate that miRNAs are crucial regulators of EMT and that their pleotropic actions during EMT and MET have important consequences for cancer progression.